Curvilinear peristaltic pump

ABSTRACT

A curvilinear peristaltic pump for pumping liquids through a resilient tube. The pump includes a curved concave platen against which a resilient tube is placed. A multi lobed cam is positioned adjacent to the platen and tube. A plurality of pump fingers are mounted between the tube and cam in a manner permitting radial movement of the pump fingers. As the cam rotates, the fingers are pressed toward the tube sequentially so as to pump liquid through the tube. The lobe end presses the tube sufficiently to occlude the tube and prevent back flow without over pressing and damaging the tube. A transverse pinch finger is provided on each pump finger, extending from the tube pressing face of each pump finger. At the tube occluding position, the pump finger nearly occludes the tube and the pinch finger completes occlusion without pressing the tube beyond the fully occluded position. A fixed or slidable spring pressed pinch finger may be used.

BACKGROUND OF THE INVENTION

This invention relates in general to fluid pumps and more specificallyto a peristaltic pump having a cam driven plurality of fingers forsequentially engaging a resilient tube to create liquid flow through thetube.

Conventional linear and rotary peristaltic pumps typically have asection of resilient tubing positioned between a wall and a set ofrollers or reciprocating pushers that progressively compress sections ofthe tubing to pump liquids. Such pumps are often used in medicalapplications, such as intravenous infusion or withdrawing fluids such asin a wound drainage system. These pumps operate in a positive manner andare capable of generating substantial outlet pressures.

Typical linear peristaltic pumps include those described by Sorg et al.in U.S. Pat. No. 2,877,714, Borsannyi in U.S. Pat. No. 4,671,792Heminway et al. in U.S. Pat. No. 4,893,991 and Canon in U.S. Pat. No.4,728,265. While generally effective, these pumps are large, complex andcumbersome, requiring a drive shaft parallel to a resilient tube and aplurality of cams along the drive shaft to move pushers toward and awayfrom the tube.

Rotary peristaltic pumps generally dispose a resilient tube along acircular path, with a number of rollers mounted around the circumferenceof a circular rotor sequentially rolling along the tube to occlude thetube and force liquid through the tube. Typical of such pumps are thosedisclosed by Soderquist et al. in U.S. Pat. No. 4,886,431 and Kling inU.S. Pat. No. 3,172,367. These pumps often have relatively lowefficiency and impose high shear and tension stresses on the tubecausing internal tube wall erosion or spallation. The tube mayeventually be permanently deformed so that the tube becomes flattenedinto a more oval shape and carries less liquid.

Another type of peristaltic pump has a tube arranged along a circularpath with a cam member within the circle sequentially moving a pluralityof blunt pushers or fingers outwardly to sequentially compress the tubefrom one end of the path to the other. Typical of these pumps are thoseshown by Gonner in German Patent No. 2,152,352 and Tubospir in ItalianPatent No. 582,797.

These pumps tend to be less complex than linear peristaltic pumps.However, the pressure imposed by the blunt fingers reduces tube life,sometimes causing internal tube wall erosion or spallation, whichresults in particulate matter getting into the fluid stream. Tube withdifferent wall thicknesses cannot be accommodated by these pumps, sincewith thinner than standard tubes the fingers will not properly occludethe tube and with thicker than standard tubes the tube will closeprematurely and be subject to excessive compression, requiring highercam drive power and causing excessive wear on the cam and tube.

Thus, there is a continuing need for peristaltic pumps of greatersimplicity, small size, low drive power requirements and which canaccommodate resilient tubes of varying wall thickness while reducingwear and internal erosion of the resilient tube.

SUMMARY OF THE INVENTION

The above-noted problems, and others, are overcome in accordance withthis invention by a curvilinear peristaltic pump having a concavecurved, generally circular, platen for supporting a resilient tube, amulti-lobe cam rotatable about the center of the platen concavity, and aplurality of pump fingers riding on the cam as cam followers and guidedto move in a radial direction toward and away from said platen.

Each pump finger has a face for engaging a tube on said circular platen.Each face includes a narrow pinch finger spring centered in the face andbiased to extend beyond the face. Further, each pump finger includes aroller between the body of the pump finger and the cam to ride on thecam in the manner of a roller bearing, reducing wear.

When the cam is rotated, the pump finger closest to the highest area onthe cam (widest lobe) in the direction of rotation will be movedoutwardly in a radial direction to squeeze the tube against the platen.As the cam continues to rotate, the second pump finger will squeeze thetube as the pinch finger on the first pump finger occludes the tube, toforce liquid in the tube to flow in the same direction as the camrotates. As cam rotation continues, the subsequent fingers willsequentially squeeze the tube to push liquid and then occlude the tube.At the same time, the pump finger just behind the lobe will move awayfrom the tube, allowing the tube to expand and fill with liquid. Thissequence continues as cam rotation proceeds.

BRIEF DESCRIPTION OF THE DRAWING

Details of the invention, and of preferred embodiments thereof, will befurther understood upon reference to the drawing, wherein:

FIG. 1 is a perspective view of my pump with the casing open andpartially cut-away and one pump finger and pinch finger cut-away;

FIG. 2 is a side elevation of the pump at the beginning of a pumpingcycle with the casing closed and the near side casing removed to showthe internal components;

FIG. 3 is a detail side elevation view of the pump finger assemblyhaving a spring biased pinch finger and with the pinch finger partiallycut-away; and

FIG. 4 is a detail side elevation view of a pump finger with analternate pinch finger embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, there is seen a curvilinear peristaltic pump10 having a casing basically consisting of a front plate 12, a backplate 14 and spacers 16. The casing is held together by a plurality ofbolts 19 for ease of assembly and disassembly as needed. A removablecover 18 is secured to casing 10. Each spacer 16 includes a block 20having a hole therethrough cooperating with a pin or bolt 22 andhook-shaped cover extensions 24 to hold the cover 18 in place.

Cover 18 includes a concave curvilinear platen 26. While platen 26 mayhave any suitable surface, generally a cylindrical surface is preferred.As best seen in FIGS. 2 and 3, a resilient tube 28 may be laid alongplaten 26, exiting through the open space between each pair ofextensions 24.

A multi-lobed cam 30 is mounted for rotation about an axle 32 thatextends through suitable bearings in front and back plates 12 and 14.Cam 30 may have any suitable number of lobes, two or more. For optimumperformance with smallest size, the three-lobe cam shown is preferred.Where platen 26 is cylindrical, axle 32 is preferably at the axis of theplaten. Cam 30 can be rotated in either direction to pump liquid throughtube 28 in either direction. For convenience of operation explanation,cam 30 will be considered to be rotating clockwise, as indicated byarrow 34. Any suitable drive means may be used to rotate cam 30. In thepreferred embodiment shown, an electric drive motor 36 extends throughopening 37 in back plate 14 and is mounted on the back surface of frontplate 12. Motor 36 has a drive shaft 38 extending through front plate 12to a pulley 40. A drive belt 42 extends from pulley 40 to pulley 44mounted on cam axle 32. Pulleys 40 and 44 are sized to provide thedesired cam rotation speed. A variable speed motor 36 may be used toallow cam rotation speed to be easily varied. If desired, a gear systemcould be used in place of belt 42, or a different drive system could beused, such as a conventional hydraulic drive, in place of the electricmotor and belt drive system shown.

A plurality of pump fingers 48, as best seen in FIGS. 1 and 3, aremounted for radial movement on front plate 12 and back plate 14 betweencam 30 and platen 26. Any suitable number of pump fingers 48 may beused. Where a greater number of cam lobes are used, fewer fingers willgenerally be used. On the other hand, if narrow fingers 48 are used, alarger number may be provided. A large scale pump will generally use alarger number of fingers. A preferred number of pump fingers 48 for athree-lobe cam 30 of maximum efficiency coupled with small size is from7 to 11 pump fingers, with 9 generally being optimum. As seen in FIG. 1,a plurality of opposed radial grooves 50 are provided in front plate 12and back plate 14 to receive side extensions 52 that extend into grooves50 and are freely movable therealong.

Each pump finger 48, as best seen in FIG. 3, includes a cylindricalrecess 54 at a first end 56 for rotatably receiving a bearing roller 58.Rollers 58 freely roll on the surface of cam 30 in the manner of rollerbearings, reducing wear on the cam surface. Side extensions 52 as seenin FIG. 1 are formed on the sides of pumping finger 48. A transverse,inverted "T" slot 62 is formed across the top of pump finger 48. A base64 mounting a transverse pinch finger 66 fits within slot 62, with pinchfinger 66 extending through a transverse cavity in the pumping surfacealong second end 68 of pump finger 48, as seen in FIG. 1. A spring 70biases base 64 and pinch finger 66 toward the extended position.

The pump operates in the following manner. As seen in FIG. 2, two lobesof cam 30 are located at the beginning and end of the series of pumpfingers 48. At this position, pump fingers 48 engaging the centralportion of tube 28 along the middle of platen 26 are relativelywithdrawn and those at the ends are relatively extended, therebycreating a zone of occlusion. Thus, the central portion of tube 28 isfilled with liquid and the ends are substantially occluded. As cam 30rotates in the direction of arrow 34, the second left pump finger 48 ispressed further against tube 28 while the rightmost pump finger beginsto withdraw. Liquid is thus pushed in a zone of occlusion toward theright or outlet end of tube 28 and begins to exit. As cam rotationcontinues, pump fingers 48 are sequentially extended from the left andwithdrawn at the right, forcing liquid in tube 28 toward the outlet end.

As seen in the central region of tube 28 in FIG. 2, pinch fingers 66under the forces of springs 70 are relatively extended. The leftmostpump finger 48 is slightly extended, but second end 68 of pump finger 48has not entirely occluded tube 28. Pinch finger 66 is extendedsufficiently under the force of spring 70 to occlude the tube. With athin wall tube 28, pinch fingers 66 will extend further to close thetube. With a thick walled tube, pinch finger will only extend a shorterdistance until the tube is closed. Thus, only enough force is appliedthrough the pinch finger to close the tube.

In prior art pumps, the pumping finger extended only a single presetdistance under the strong mechanical force of a cam. With thosearrangements, thin tubes are not entirely occluded and thick walledtubes are crushed beyond closure, often resulting in rapid wear,internal wall erosion and spallation with the resulting injection ofparticles of wall material into the liquid stream, of great concern inmany infusion operations. Only a short degree of extension andretraction of pinch fingers 66 is required to produce this highlyadvantageous result, typically from about 0.2 to 1.0 mm.

FIG. 4 shows a side elevation view of a second embodiment of pumpfingers 48. Here the pump fingers 48 use a pinch finger in the form of afixed transverse ridge 71 across the surface 68 of the pump fingers inplace of the spring biased pinch fingers 66 of the embodiment of FIG. 3.While the FIG. 3 embodiment is generally preferred for lowest tube wearand the ability to work well tubes of slightly varying diameter and wallthickness, in other cases the lower cost version of FIG. 4 may bepreferred where the tube is more dimensionally uniform or the motor hassufficient power and the tube can take greater compression.

While certain specific relationships, materials and other parametershave been detailed in the above description of preferred embodiments,those can be varied, where suitable, with similar results. Otherapplications, variations and ramifications of the present invention willoccur to those skilled in the art upon reading the present disclosure.Those are intended to be included within the scope of this invention asdefined in the appended claims.

I claim:
 1. A curvilinear peristaltic pump which comprises:a curved,concave, platen; a rotatable cam spaced from said platen; means forrotating said cam in a first direction; a plurality of pump fingers,each having a first end riding on said cam and a second end adjacent tosaid platen; guide means for axially guiding said pump fingers in radialdirections; said cam configured to first sequentially move said pumpfingers toward said platen and second sequentially allow said pumpfingers to move away from said platen; each of said pump fingers havinga pinch finger extending beyond said second end, transversely acrosssecond end; whereby a resilient tube may be interposed between saidplaten and said second pump finger ends so that as said pump fingers aresequentially moved toward said platen, liquid in said tube will bepumped in said first cam rotation direction and each pinch finger willocclude said tube when each said pump finger reaches a position closestto said platen.
 2. The curvilinear peristaltic pump according to claim 1wherein each said pinch finger comprises a slidable member extendingthrough a transverse slot in each pump finger second end and furtherincluding means for biasing each said pinch finger in a directionextending outwardly of said transverse slot.
 3. The curvilinearperistaltic pump according to claim 2 wherein each of said pump fingershas a transverse cavity communicating with said transverse slot, a basemember within said cavity supporting a pinch finger in said transverseslot, with a compression spring between said base member and a wall ofsaid cavity opposite said pinch finger.
 4. The curvilinear peristalticpump according to claim 1 wherein each said pinch finger is a transverseridge on each said pump finger second end.
 5. The curvilinearperistaltic pump according to claim 1 wherein each of said cams has atleast two lobes and has a surface gradually transitioning between lobes.6. The curvilinear peristaltic pump according to claim 1 wherein eachpump finger carries a rotatable roller at said first end to engage androll along said cam.
 7. The curvilinear peristaltic pump according toclaim 1 further including releasable latch means for attaching saidplaten to a cam support casing.
 8. The curvilinear peristaltic pumpaccording to claim 1 wherein said platen surface is cylindrical and saidcam is rotatable around an axis concentric with said cylindrical platensurface.
 9. The curvilinear peristaltic pump according to claim 1wherein said cam is supported for rotation between parallel front andback plates.
 10. The curvilinear peristaltic pump according to claim 9wherein said guide means comprises cooperating pairs of radial groovesin said front and back plates and side extensions on each pump fingerfor radial sliding in a pair of said grooves.
 11. A curvilinearperistaltic pump which comprises:a curved, concave, platen; a rotatablemulti-lobed cam spaced from said platen; means for rotating said cam ina first direction; a plurality of pump fingers, each having a first endriding on said cam and a second end adjacent to said platen; guide meansfor axially guiding said pump fingers in radial directions from a centerof rotation of said cam; a resilient tube interposed between said platenand said pump fingers; said cam configured to first sequentially movesaid pump fingers toward said platen to compress said tube and secondsequentially allow said pump fingers to be moved away from said platenby tube resiliency; each of said pump fingers sized to compress saidtube as said cam moves said pump fingers forward said platen but notfully occlude said tube; and each of said pump fingers having a pinchfinger extending transversely beyond said pump finger second end tofully occlude said tube as said cam moves said pump fingers toward saidplaten.
 12. The curvilinear peristaltic pump according to claim 11wherein each said pinch finger comprises a slidable member extendingthrough a transverse slot in each pump finger second end and furtherincluding means for biasing each said pinch finger in a directionextending outwardly of said transverse slot.
 13. The curvilinearperistaltic pump according to claim 11 wherein each said pinch finger isa transverse ridge on each said pump finger second end.
 14. Thecurvilinear peristaltic pump according to claim 11 wherein said cam hasat least two spaced lobes and cam diameter smoothly changes diameterfrom widest at said lobes to narrower between said lobes.
 15. Thecurvilinear peristaltic pump according to claim 11 wherein each pumpfinger carries a rotatable roller at said first end to engage and rollalong said cam.
 16. The curvilinear peristaltic pump according to claim11 further including releasable latch means for attaching said platen toa cam support casing.
 17. The curvilinear peristaltic pump according toclaim 11 wherein said platen surface is cylindrical and said cam isrotatable around an axis concentric with said cylindrical platensurface.
 18. The curvilinear peristaltic pump according to claim 11wherein said cam is supported for rotation between parallel front andback plates.
 19. The curvilinear peristaltic pump according to claim 18wherein said guide means comprises cooperating pairs of radial groovesin said front and back plates and further including side extensions oneach pump finger for radial sliding in a pair of said grooves.
 20. Thecurvilinear peristaltic pump according to claim 11 wherein each of saidpump fingers comprises an elongated body having a transverse slot acrosssaid second end, extending into said pump finger and communicating witha cavity, said pinch finger slidably fitting within said slot andsecured to a base in said cavity and further including a compressionspring between said base and a wall of said cavity opposite said pinchfinger to bias said pinch finger outwardly of said transverse slot.